Huntley Meadows Hemi-Marsh Restoration

WSSI, in partnership with Fairfax County Park Authority (FCPA), used innovative engineering practices to restore the wetland areas of Huntley Meadows hemi-marsh, an extremely sensitive environment, to ensure the ecological goals of the County were successfully met.

The Challenge

Huntley Meadows Park is a highly prized and protected natural resource in a densely urbanized area. Since the late 1970s, the central wetland area of the park has been notable as the largest non-tidal wetland in northern Virginia. Beaver damming changed the water flow, and the wetland transitioned into a hemi-marsh. Hemi-marshes are one of the most ecologically productive and diverse ecosystems and are unusual as they feature fluctuating water levels.

The hemi-marsh went through a long decline due to a uniform and unmanageable water level, siltation from upstream development, natural succession, and impacts from Canada goose herbivory. Large monotypic stands of invasive species dominated the wetland and greatly reduced wildlife habitat diversity and ecological function. After two unsuccessful restoration attempts by others, the FCPA contracted WSSI in 2011 to restore the central wetland area as a hemi-marsh.

Our Solution

WSSI faced the significant engineering challenge of raising the permanent water surface elevation while providing the ability to accurately control the water level. WSSI designed control structures to provide this necessary flexibility, including a ±450-foot earthen berm with a vinyl sheet-pile core (to prevent short-circuiting through the dam) which could be overtopped in larger storm events, along with a concrete riser equipped with adjustable slide gates to provide maximum flexibility in controlling the elevation of the normal pool of the impoundment. The park has long been beloved by the community and restoration and protection of the central wetland was a rallying point. Today the hemi-marsh system is thriving and is accessible to visitors with a trail system. WSSI worked with the FCPA and community leaders to ensure all stakeholders were informed and engaged in the process of restoring this “crown jewel” (as it is often called) of the Fairfax County Park System.

Awards

• Engineering Excellence Awards – National Recognition, Water Resources Category (2014), American Council of Engineering Companies
• Engineering Excellence Honor Award (2013-2014), American Council of Engineering Companies of Metro. Washington
• Environmental/Conservation Award (2016), National Association of County Park and Recreation Officials (with FCPA)
• Best Protected Environmentally Sensitive Site, Land Conservation Awards (2013), Fairfax Co., VA
• Outstanding Commitment to Tree Preservation, Tree Conservation Awards (2014), Fairfax Co., VA